1. Field of the Invention
This invention relates to power transmission systems which provide a range of gear ratios in discrete steps.
2. Description of the Prior Art
Manually-shifted transmissions continue to offer a substantial fuel economy advantage in comparison to the production automatic transmissions currently available in passenger cars and trucks. On the other hand, not even the most skillful driver can begin to match the consistent precision with which current automatic transmissions perform downshifts uncompromised by any interruption in engine power output. In fact, the level of skill required for smoothly downshifting a conventional manual transmission often discourages drivers from downshifting in order to elevate engine power output above the range normally used for vehicle cruising. In particular, even experienced drivers have difficulty judging the proper amount by which to elevate engine speed before re-engaging the clutch to complete the downshift. In the case of truck transmissions, added skill is often required because synchronized gearshifting is commonly restricted to transmissions having seven or fewer forward speed ratios. While progress has been made in automating the gearshifting sequence of manual truck transmissions, these transmissions are expensive and unproven in the domestic market.